Technical Abstract:
Strawberry plants exhibiting symptoms of stunting and abnormally small leaves were observed in production fields in central Florida. Since the symptoms were suggestive of possible phytoplasma infection, plants were assayed for presence of phytoplasma by polymerase chain reaction (PCR) amplification of 16S rDNA and ribosomal (r) protein (p) gene sequences. Amplification of phytoplasma-specific DNA sequences in PCR indicated infection of the diseased strawberry plants by phytoplasma. RFLP analyses of amplified 16S rDNA revealed that the plants were infected by two mutually distinct phytoplasmas that differed from strawberry green petal phytoplasma (group 16SrI-C). Both phytoplasmas were members of 16S rRNA gene group I (16SrI). Based on RFLP analysis of 16S rDNA and rp gene sequences, one was classified in group 16SrI subgroup I and new rp subgroup 16SrI- I(rp); its 16S rRNA-ribosomal protein subgroup was designated 16SrI-K(rr-rp). The second phytoplasma represented a previously undescribed subgroup, designated K, in 16S rRNA group I but belonged to rp subgroup 16SrI- E(rp); this phytoplasma's 16S rRNA-ribosomal protein subgroup was designated 16SrI-J(rr-rp). Further evidence indicated that the 16SrI-K(rr-rp) strawberry phytoplasma, Mexican periwinkle virescence phytoplasma, and stolbur phytoplasma shared sequence homologies that enabled amplification of DNA from all three in PCR using primers previously designed as stolbur-specific.